For example, there are known continuous cored electrodes for CO.sub.2 welding, the core material of which electrodes include deoxidizing as well as slag-forming elements, and a stabilizing agent/cf. U.S.S.R. Inventor's Certificate No. 285,801, No. 312,717, France Pat. No. 1,517,199, U.S. Pat. No. 3,418,446.
Excellent welding performance and reliable weld forming as well as insignificant spattering of metal during welding operation, are the features inherent in continuous cored electrodes, in which the core material includes titania rutile, and which are disclosed in U.S.S.R. Inventor's Certificate No. 285,801, and in U.S. Pat. No. 3,418,446.
The cored electrode described in the U.S.S.R. Inventor's Certificate No. 285,801 referred to above comprises a tubular sheath enclosing core material containing the following ingredients, in percent by weight:
______________________________________ Rutile from 20 to 40 Ferromanganese from 10 to 13 Feldspar from 0.6 to 6.0 Sodium flousilicate from 0.6 to 4.5 Ferrosilicon from 0.6 to 2.0 Iron powder the balance. ______________________________________
According to the aforecited U.S. Pat. No. 3,418,446, the continuous cored electorde comprises a tubular sheath enclosing granular core material containing the following ingredients:
______________________________________ Percent by weight of the total core ______________________________________ Rutile 55 Ferrosilicon 14 Manganese 16 Magnetite 15 ______________________________________
The known cored electrodes, if utilized for CO.sub.2 welding of metal constructions using up to 800 amperes and a welding rate of 100 meters per hour, display a number of basic disadvantages, namely:
the formation of filled weld, using a current of over 500 amperes, turns out unsatisfactory because of weld upsets and undercuttings which appear respectively, at welding rates of up to 50 m/hr and over 70 m/hr;
welding with the known cored electrodes, using over 600 amperes, does not ensure high weld bend ductility, and in particular, weld impact resistance at negative temperatures.
The elimination of the non-uniform fusion of the electrode core and sheath is generally effected in the following manner:
first, either by using electrode wires with a complex-shaped sheath, twin wire electrode cf. U.S.S.R. Inventor's Certificate No. 203,111;
or by using iron powder as the ingredient of the electrode core material.
In the first instance, the process of making such cored electrodes becomes more complicated, the second one suffering from a number of disadvantages, namely:
potential content of gases is increased in the electrode core, said gases, such as oxygen, nitrogen and hydrogen, being introduced therein by the iron powder, which impairs mechanical properties of both the weld metal and weld seam;
because of the developed contact surface of the iron powder, and due to the presence of the oxidized layer on the surfaces of particles, electric resistance of the electrode core remains considerably high as compared to that of the core sheath, resulting in non-uniform fusion of the core sheath and material.
The primary object of the present invention is to provide a continuous cored electrode which makes it possible to eliminate non-uniform fusion of the core sheath and material.
Another object of the invention is to provide a continuous cored electrode which ensures satisfactory formation of fillet welds under heavey-duty welding conditions.
Still another object of the invention is to provide a continuous cored electrode which provides for higher weld and metal weld impact resistance under heavy-duty welding conditions.
These and other objects and advantages of the invention are attained in a continuous cored electrode comprising a low-carbon steel sheath member and a core in the form of granular material including the following ingredients: feldspar, sodium fluosilicate, ferromanganese, ferrosilicon, and reduced titanium concentrate, said ingredients being present in the following amounts:
______________________________________ Percent by weight of the total core ______________________________________ Feldspar from 1.8 to 10.4 Sodium fluosilicate from 1.6 to 10.0 Ferromanganese from 13.0 to 20.0 Ferrosilicon from 0.6 to 1.6 Reduced titanium concentrate from 58 to 83 ______________________________________
With the purpose of increasing both the weld, and weld bend ductility, the electrode core material additionally contains ferrotitanium in an amount of 2.6 to 5.2 percent by weight, the remaining ingredients being present in the following amounts:
______________________________________ Percent by weight of the total core ______________________________________ Feldspar from 2.2 to 10.1 Sodium fluosilicate from 1.6 to 10.6 Ferromanganese from 13.0 to 20.0 Ferrosilicon from 0.6 to 1.6 Reduced titanium concentrate from 53 to 80. ______________________________________
It is known that reduced titanium concentrate is made up of transition titanium oxides, 70-75 wt.%, such as Ti.sub.3 O.sub.5 and Ti.sub.4 O.sub.7, which differ from TiO.sub.2, titanium dioxide, the base component of rutile, in that said oxides show higher electric conductivity by 10.sup.6 times. This factor makes it possible to eliminate non-uniform fusion of the electrode core material during a welding process employing a current of up to 800 amperes. The reduced titanium concentrate also contains metallic iron, 20-25 wt.% characterized by high dispersity and uniform distribution in the grains of the base. The presence of metallic iron enables the amount of deposited metal to be increased. The reduced titaium concentrate in the indicated amount provides for satisfactory weld formation and a stable arc accompanied by insignificant metal spattering, even when using currents of up to 800 amperes, while making best use of improved working properties of slag, such as its covering ability and an optimum crystallization range. The aforesaid property of the reduced titanium concentrate has been found to be effective when used as a part of the core material in combination with feldspar contained in the amount mentioned above. In addition, being high in potassium and sodium oxides the feldspar functions to stabilize welding arc.
The sodium fluosilicate, contained in the core material, functions to bond the hydrogen, present in the arc burning zone, into an insoluble in molten metal fluohydric compound. The presence of sodium fluosilicate in the core material in the amount indicated results in the formation of porosity caused by hydrogen; of the sodium fluosilicate content exceeds that mentioned above, the arc burning stability is impaired and the electrode metal spattering is increased.
The ferromanganese and ferrosilicon present in the aforecited amounts provide for deoxidation and alloying processes required for obtaining prescribed weld strength and bend ductility characteristics. The ferrotitanium, when present in the indicated amount, enables refinement of the metal weld structure, thus increasing ductility, or weld impact resistance.